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Deadly Virus to Control Invasive Carp in Australia

Suppose that the ornamental aquatic industry were to suggest the release of a deadly virus into native waters to control the spread of an invasive fish species. Surprising though it might appear at first sight, this precise situation is real.


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John Dawes

Let’s suppose that the ornamental aquatic industry were to suggest the release of a deadly virus into native waters to control the spread of an invasive fish species. What do you think the reaction of the authorities and conservation or recreational agencies would be? It seems reasonable to imagine the industry being accused of irresponsibility toward the welfare of indigenous fish fauna, the environment and, probably, much else.

Surprising though it may appear at first sight, this precise situation is real, with a very important difference. The case for release of the deadly cyprinus herpesvirus 3 (CyHV-3) pathogen, which causes koi herpesvirus disease, is not being made by our industry but by a coalition of conservationists, recreational fishermen and farmers that is pressing Australia’s federal and state governments to eliminate invasive common carp (Cyprinus carpio) from the Murray River.

Carp first were released accidentally in the 1960s, and since then the species has proliferated at an alarming rate; it now represents a serious threat to native fishes of the Murray-Darling Basin as well as the waterways themselves. Tests carried out over the past seven years at the Commonwealth Scientific and Industrial Research Organisation’s (CSIRO) Animal Health Laboratory have shown that CyHV-3 can act as an efficient method of carp control, taking just over a week to kill its victims.

According to the laboratory’s scientists, the virus does not appear to affect Australia’s native fish species or other introduced species. It also appear to have no affect on birds, amphibians, reptiles or mammals, including humans. Therefore, the release of the virus appears to hold promise as an effective method of eliminating the invasive carp.

Because koi belong to the same species as the common carp, the virus would control any escapes of these colorful fish as well. We already know just how lethal the virus has been, and continues to be, since it first emerged in Israel in the 1980s. It might not be 100 percent effective, but it still kills between 70 and 90 percent of affected fish.

Completion of the testing, headed by CSIRO’s senior research veterinarian Dr. Ken McColl, was expected by the end of 2015, after which it was hoped that the lengthy preparations for the release program could begin. As I write, the Invasive Animals Cooperative Research Centre in Canberra is preparing a release proposal for government approval. We now await further news regarding the approval, postponement or rejection of that proposal. Of the three options, the first appears most likely at this stage.

Returning to my opening paragraph, while our industry likely would have been accused of crimes if we proposed the virus’ release, we mustn’t overreact at the strategy envisaged by the Australian authorities, whenever the imminent release is announced. Instead, we need to take into account the fact that Australia probably has the most stringent fish health controls in the world. This does not mean that we should be complacent, because important questions arise with regard to Australia’s koi breeding sector.

How, for example, can koi breeders protect their businesses and fish stocks if approval is granted for the release of the virus? Renowned Australian ornamental fish expert and commentator Norm Halliwell of the Riverside Aquarium and Cichlid Centre posed this and other questions in a lengthy letter to New South Wales (NSW) Government’s Department of Primary Industries, Fishing and Aquaculture.

In his detailed and informative response to this particular question, Bob Creese, NSW’s director of fisheries research, said: “… there is still a long process to be undertaken before biological control of carp might be possible in Australia … there is a need to undertake a thorough risk-assessment process to explore any risks that might arise through the use of the virus, and strategies to overcome them. There is also a need to undertake extensive stakeholder consultation … (If the release is approved) … it will be important that koi breeders, retailers and enthusiasts employ effective biosecurity measures to protect their fish … NSW Department of Primary Industries will be consulting with koi breeders…to develop a biosecurity plan to help them safeguard their business and fish from the virus… .”

On the question of the transfer of the virus by birds on their feathers or feet, Creese said, “the risk of CyHV-3 being transferred between waterbodies … is likely to be remote.” In visits to numerous U.K. recreational fisheries affected by the virus, researchers found no evidence of transfer, even in those cases where “the affected fisheries were adjacent to bodies of water that never experienced a CyHV-3 outbreak, despite being separated by only 3 to 4 metres of grassy embankment with populations of waterfowl moving between waterbodies in an unrestricted manner.”

So, despite the alarming nature of the headline-grabbing news of an impeding release of a deadly virus, we must acknowledge that the Australian authorities currently are not rushing things. This, coupled with the promise of thorough consultation with stakeholders, obviously including the Australian ornamental aquatic sector, seems to provide breathing space for a thorough examination and debate of the whole subject. A solution undoubtedly will be found. Let’s just hope that Australia’s koi breeders don’t end up on the losing side and that some form of a win-win outcome will occur. 

 

This article originally appeared in the May 2016 issue of Pet Product News.

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